The present disclosure relates to implantable medical devices such as fluid flow control devices including adjustable valves and also relates to tools for determining the location and settings of an adjustable valve. More particularly, the present disclosure relates to tools for finding the magnetic center and indicating a setting of an implantable adjustable valve.
Generally, a fluid flow control device includes a one-way control valve for controlling the flow of cerebrospinal (CSF) fluid out of a brain ventricle and preventing backflow of fluid into the brain ventricle. Hydrocephalus, a neurological condition which may affect infants, children and adults, results from an undesirable accumulation of fluids, such as CSF, within the ventricles, or cavities, of the brain and which accumulation may exert extreme pressure with brain and skull deforming forces, the latter in infants. Treatment of hydrocephalus often involves draining CSF away from the brain ventricles utilizing a drainage or shunt system including one or more catheters and a valve which may generally be described as a fluid flow control device or shunt valve. The shunt valve, or fluid flow control device, may have a variety of configurations and may be adjustable in that the valve mechanism of the device may be set to a threshold pressure level at which fluid may be allowed to begin to flow through the valve and drain away from the brain. Shunt valves may be subcutaneously implantable and percutaneously adjustable to various pressure settings. Examples of fluid flow control devices are disclosed, for example, in U.S. Pat. No. 5,637,083 entitled, “Implantable Adjustable Fluid Flow Control Valve”, and U.S. patent application Ser. No. 13/804,875 entitled, “Fluid Flow Control Devices, Rotors and Magnets with Increased Resistance to Inadvertent Setting Change and Improved Accessory Tool Coupling”, incorporated by reference herein in their respective entireties.
Adjustable valves may include magnetic components which allow an external tool or tools to selectively and non-invasively determine the setting of the implanted valve and adjust the setting to a desired pressure. A tool set typically includes: a locator tool, which allows tactile determination of the orientation and position of the implanted valve; an indicator tool, to determine the current setting of the adjustable valve and confirm new settings of the valve after the new settings have been implemented; and an adjustment tool to change the setting of the valve. The tools are designed to externally (i.e., external to a patient) couple with a magnet of the adjustable valve such that upon coupling, the setting of the valve may be determined and the valve magnet may be deliberately manipulated to thereby adjust the pressure setting of the valve without removal of the subcutaneously implanted device. Indicator and adjustment tools thus rely on magnetic coupling of the tool to the adjustable valve, where the magnetic coupling is strong enough to determine or to adjust the position of the valve magnet even through tissue (e.g., a patient's scalp). Examples of locator, indicator and adjustment tools are shown, for example, in U.S. Patent Application Publication No. 2002/0022793 (hereinafter, “the '793 application”) to Bertrand et al. entitled, “Tool for Adjusting an Implantable Adjustable Fluid Flow Control Valve” and U.S. Pat. No. 6,883,241 to Moskowitz, et al., entitled, “Compass-Based Indicator with Magnetic Shielding”, incorporated by reference herein in their respective entireties.
Locator, indicator and adjustment tools may be used in conjunction with one another. For example, after the tactile determination of a valve's position has been made in conjunction with a locator tool, an indicator and/or adjustment tool may be positioned in a location determined by the locator tool. In other words, an indicator and/or adjustment tool position may be based off of or may be “keyed to” the locator tool position. The position of an adjustable valve, as determined by the locator tool, allows the indicator and/or adjustment tools to be placed in sufficient proximity to the magnetic components of the implanted valve such that the valve magnet or magnets align and/or couple with the magnetized tool elements or magnets. However, the magnetized element of an indicator tool may tend toward alignment with the earth's magnetic field if the pull of the magnet in the implanted valve is not sufficiently strong (such as when the distance between the implanted valve magnet or magnets and the tool increases) and could lead to inaccurate device setting determinations or indications.
In addition, magnetic components of the adjustable valve itself may be susceptible to movement or inadvertent setting adjustment by strong nearby magnetic fields since the internal magnetic elements of a valve may tend to align with an external field. An adjustable valve might therefore be unintentionally adjusted when in the presence of a strong external magnetic field, such as encountered in a magnetic resonance imaging (MRI) procedure. Thus, some fluid flow control devices include features which provide increased resistance to inadvertent setting changes. For example, mechanical “stops” or magnet configurations designed to resist strong nearby magnetic fields may be incorporated into a device such as disclosed, for example, in U.S. patent application Ser. No. 13/804,875, referred to above. Deliberate adjustment of these types of valves, in some cases, may be more difficult to achieve without an accurate alignment of the adjustment tool to the valve magnet.
In order to accurately magnetically align or couple a tool to an implanted valve (for example, to avoid effects of the earth's magnetic field on the tool or to ensure a sufficient coupling of a tool to a valve for valve setting indication and adjustment purposes), it may thus be desirable to find the magnetic center of the valve magnet and thereby position a tool in magnetic alignment with the magnetic center of the valve magnet. Aligning an external tool with the magnetic center of the valve can provide coupling of the tool to the valve which allows an accurate or more accurate reading of a valve setting and allows deliberate adjustment of the valve to be carried out, even where the distance between the implanted valve and the external tool is increased, and/or in cases where an implantable valve is designed for increased resistance to inadvertent setting changes.
The '793 publication depicts examples of tools which may be useful with an adjustable valve and which may be used in conjunction with the centering and centering-indicator tools 50, 150, 250 (FIGS. 3, 6, 7) of the present disclosure. The '793 publication describes a locator tool comprising a tube with a central opening and a slot. An index on the tube is for visually indicating the settings of a valve, e.g., 20, when the locator tool is aligned with the valve. The locator tool also includes a protrusion extending inwardly into the central body as well as a fluid flow direction indicator. An indicator tool may comprise an indicator central body a compass having a magnetized pointer, an index for indicating possible positions of the adjustable valve corresponding to the different valve settings, and a ridge for interacting with the protrusion of the locator tool.
As further described in the '793 publication, the locator central opening allows locator tool to be oriented to and aligned with an implanted valve in a predictable manner and allows the physician to palpate the implanted valve through opening. In use, after orientation of the implanted valve has been established by locator tool, indicator central body is placed within tube of locator tool. Indicator and locator tools may comprise alignment features. For example, when indicator central body is placed within tube, a ridge of the indicator tool aligns and interacts with a slot of the locator tool to precisely orient the indicator tool with the locator tool. Other alignment features of the indicator and locator tools are contemplated. In any event, placement of indicator tool into locator tool allows the indicator tool pointer to interact with and align itself with the magnet 120 of the valve 20. This will cause the pointer to point to a spot on the index indicating the position of the magnet 120 of the valve 20. The position of the magnet 120, as described above, indicates the setting of the valve.
The '793 publication further describes an adjustment tool having a magnet fixed in place in an adjustment central body, an indentation and an arrow. Adjustment central body may include a series of indentations configured to interact with a protrusion on the locator tool. Indentations may be spaced around the periphery of the adjustment central body corresponding to the location of the settings of the valve 20. In use, the adjustment tool is positioned above the locator tool with the arrow aligned with the pressure level setting on index, the pressure level setting of the valve having been determined previously by the indicator tool as described above or by other methods such as x-ray or fluoroscopy. Maintaining alignment, the adjustment tool is lowered toward the locator tool until the adjustment central body enters the tube. Where an indicator tool has been used to determine the valve setting, the indicator tool is removed prior locating the adjustment tool into the locator tool. The protrusion on the locator tool interacts with an indentation on the adjustment central body corresponding to the current valve setting. In this position, the adjustment tool magnet couples with the valve magnet and the adjustment tool is rotated so that the arrow points to the desired valve setting indicated on index.
Other examples of devices for locating, indicating and adjusting the setting of an adjustable valve are described in U.S. Pat. No. 7,334,582 to Bertrand, et. al., “Electronic Valve Reader”, U.S. Pat. No. 8,015,977 to Bertrand, et. al., “Indicator Tool for Use with an Implantable Medical Device”, and U.S. Pat. No. 8,257,296 to Bertrand et. al., “System Including an Implantable Medical Device and Electronic Valve Indicator and Locator Device”, incorporated by reference herein in their respective entireties.
U.S. Pat. No. 7,921,571 to Moureaux et al., “Device for Mechanically Locating and Reading the Setting of An Adjustable Valve” proposes a device for mechanically and reading the setting of an adjustable magnetic valve which describes a three-dimensionally pivoting compass including a needle and pin mounted on a pivot.